Communications system and method with A/D converter

ABSTRACT

A communications system includes a radio frequency identification device including an integrated circuit having a single die including a microprocessor, a receiver coupled to the microprocessor, and a backscatter transmitter coupled to the microprocessor, the integrated circuit having a digital input, and the receiver being configured to receive wireless communications from a remote interrogator; and an analog to digital converter external of the single die and having a digital output coupled to the digital input of the integrated circuit, and having an analog input configured to be coupled to an analog measuring device, wherein the radio frequency identification device is configured to transmit a signal indicative of the analog input using the backscatter transmitter. A communications method includes coupling an analog to digital converter to a radio frequency identification device.

CROSS REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation of U.S. patent applicationSer. No. 09/765,235, filed Jan. 16, 2001, entitled “CommunicationsSystem and Method with A/D Converter”, naming Scott Hahn and Mark T. VanHorn as inventors, which in turn in a continuation of U.S. patentapplication Ser. No. 09/249,287, filed Feb. 10, 1999, entitled“Communications System and Method with A/D Converter”, naming Scott Hahnand Mark T. Van Horn as inventors, which is now U.S. Pat. No. 6,198,392,the disclosures of which are incorporated by reference.

TECHNICAL FIELD

This invention relates to systems and methods for monitoring parametersand for remote data telemetry. The invention also relates to radiofrequency identification devices.

BACKGROUND OF THE INVENTION

Electronic identification devices, such as radio frequencyidentification devices (RFIDs), are known in the art. Such devices aretypically used for inventory tracking. As large numbers of objects aremoved in inventory, product manufacturing, and merchandising operations,there is a continuous challenge to accurately monitor the location andflow of objects. Additionally, there is a continuing goal to determinethe location of objects in an inexpensive and streamlined manner. Oneway of tracking objects is with an electronic identification system.

One presently available electronic identification system utilizes amagnetic coupling system. In some cases, an identification device may beprovided with a unique identification code in order to distinguishbetween a number of different devices. Typically, the devices areentirely passive (have no power supply), which results in a small andportable package. However, such identification systems are only capableof operation over a relatively short range, limited by the size of amagnetic field used to supply power to the devices and to communicatewith the devices.

Another type of wireless electronic identification system is an activewireless electronic identification system. Attention is directed towardscommonly assigned U.S. patent application Ser. No. 08/705,043, filedAug. 29, 1996, now U.S. Pat. No. 6,130,602, and incorporated herein byreference, which describes such active systems in detail. One suchsystem is sold by Micron Communications Inc., 3176 S. Denver Way, Boise,Id. 83705 under the trademark Microstamp Engine (TM). These systemsinclude integrated circuit devices which include an active transponderand are intended to be affixed to an object to be monitored. The devicesare capable of receiving and processing instructions transmitted by aninterrogator. A device receives the instruction, if within range, thenprocesses the instruction and transmits a response, if appropriate. Theinterrogation signal and the responsive signal are typicallyradio-frequency (RF) signals produced by an RF transmitter circuit.Because active devices have their own power sources, and do not need tobe in close proximity to an interrogator or reader to receive power viamagnetic coupling. Therefore, active transponder devices tend to be moresuitable for applications requiring tracking of a tagged device that maynot be in close proximity to an interrogator. For example, activetransponder devices tend to be more suitable for inventory control ortracking.

Because the Microstamp engine is capable of communications, it can beused for applications other than just inventory tracking and othertypical RFID applications.

The Microstamp engine includes an internal A/D converter used forbattery voltage sensing, but that A/D converter does not have anexternal input. A disadvantage of an internal A/D converter is that theuser does not have the opportunity to use an A/D converter with moreresolution than the internal A/D converter should the user be willing topay extra for such resolution. Additionally, during the service life ofa Microstamp engine, A/D converters may become available with higherresolution than the internal A/D converter.

SUMMARY

The invention provides a wireless identification device configured toprovide a signal to identify the device in response to an interrogationsignal. In addition, the invention provides coupling an analog todigital converter to the wireless identification device.

The invention also provides a communications system comprising a radiofrequency identification device including an integrated circuit. Theintegrated circuit has a single die including a microprocessor, areceiver coupled to the microprocessor, and a backscatter transmittercoupled to the microprocessor. The integrated circuit also has a digitalinput. The receiver is configured to receive wireless communicationsfrom a remote interrogator. The communications system further includesan analog to digital converter external of the single die. The analog todigital converter has a digital output coupled to the digital input ofthe integrated circuit, and has an analog input configured to be coupledto an analog measuring device. The radio frequency identification deviceis configured to transmit a signal indicative of the analog input usingthe backscatter transmitter.

Other aspects and implementations are contemplated.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

FIG. 1 is a high level circuit schematic showing an interrogator and aradio frequency identification device embodying the invention.

FIG. 2 is a front view of a housing, in the form of a badge or card,supporting the circuit of FIG. 1 according to one embodiment theinvention.

FIG. 3 is a front view of a housing supporting the circuit of FIG. 1according to another embodiment of the invention.

FIG. 4 is a circuit schematic of circuitry in accordance with oneembodiment of the invention.

FIG. 5 is a circuit schematic of circuitry added to the circuitry ofFIG. 4 in an alternative embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of theconstitutional purposes of the U.S. Patent Laws “to promote the progressof science and useful arts” (Article 1, Section 8).

FIG. 1 illustrates a wireless identification device 10 in accordancewith one embodiment of the invention. In the illustrated embodiment, thewireless identification device is a radio frequency data communicationdevice 10, and includes RFID circuitry 12. The device 10 furtherincludes an antenna 14 connected to the circuitry 12 for wireless orradio frequency transmission by the circuitry 12 and an antenna 15coupled to the circuitry 12 for wireless or radio frequency reception bythe circuitry 12. In one embodiment, the antennas 14 and 15 aremicrostrip antennas. In the illustrated embodiment, the RFID circuitry12 is defined by an integrated circuit as described in theabove-incorporated patent application Ser. No. 08/705,043, filed Aug.29, 1996, now U.S. Pat. No. 6,130,602. Other embodiments are possible. Apower source or supply 16 is connected to the integrated circuit 12 tosupply power to the integrated circuit 12. In one embodiment, the powersource 16 comprises a battery.

The device 10 transmits and receives radio frequency communications toand from an interrogator 18. An exemplary interrogator is described incommonly assigned U.S. patent application Ser. No. 08/907,689, filedAug. 8, 1997, now U.S. Pat. No. 6,289,209, and incorporated herein byreference. Preferably, the interrogator 18 includes an antenna 20, aswell as dedicated transmitting and receiving circuitry, complementary tothat implemented on the integrated circuit 12.

Generally, the interrogator 18 transmits an interrogation signal orcommand 22 via the antenna 20. The device 10 receives the incominginterrogation signal via antenna 15. Upon receiving the signal 22, thedevice 10 responds by generating and transmitting a responsive signal orreply 24 via antenna 14. The responsive signal 24 typically includesinformation that uniquely identifies, or labels the particular device 12that is transmitting, so as to identify any object or person with whichthe device 12 is associated.

Although only one device 10 is shown in FIG. 1, typically there will bemultiple devices 10 that correspond with the interrogator 18, and theparticular devices 10 that are in communication with the interrogator 18will typically change over time. In the illustrated embodiment in FIG.1, there is no communication between multiple devices 10. Instead, thedevices 10 respectively communicate with the interrogator 18. Multipledevices 10 can be used in the same field of an interrogator 18 (i.e.,within communications range of an interrogator 18).

The device 10 can be included in any appropriate housing or packaging.Various methods of manufacturing housings are described in commonlyassigned U.S. patent application Ser. No. 08/800,037, filed Feb. 13,1997, now U.S. Pat. No. 5,988,510, and incorporated herein by reference.

FIG. 2 shows but one embodiment in the form of a card or badge 26including a housing 28 of plastic or other suitable material supportingthe device 10 and the power supply 16. In one embodiment, a face of thebadge 26 has visual identification features such as graphics, text,information found on identification or credit cards, etc.

FIG. 3 illustrates but one alternative housing supporting the device 10.More particularly, FIG. 3 shows a miniature housing 28 encasing thedevice 10 and power supply 16 to define a tag which can be supported byan object (e.g., hung from an object, affixed to an object, etc.).Although two particular types of housings have been disclosed, otherforms of housings are employed in alternative embodiments.

If the power supply 16 is a battery, the battery can take any suitableform. Preferably, the battery type will be selected depending on weight,size, and life requirements for a particular application. In oneembodiment, the battery 16 is a thin profile button-type cell forming asmall, thin energy cell more commonly utilized in watches and smallelectronic devices requiring a thin profile. A conventional button-typecell has a pair of electrodes, an anode formed by one face and a cathodeformed by an opposite face. In an alternative embodiment, the powersource 16 comprises a series connected pair of button type cells. Inother alternative embodiments, other types of suitable power source areemployed.

The circuitry 12 provides a responsive signal to the interrogator 18 byradio frequency. More particularly, the circuitry 12 comprises anintegrated circuit including a single die having a backscattertransmitter 30, a receiver 32, a memory 34, and a microprocessor 36coupled to the transmitter 30, receiver 32, and memory 34 (FIG. 1) as isdescribed in U.S. patent application Ser. No. 08/705,043, filed Aug. 29,1996, now U.S. Pat. No. 6,130,602.

Radio frequency identification has emerged as a viable and affordablealternative to tagging or labeling small to large quantities of items.The interrogator 18 communicates with the devices 10 via anelectromagnetic link, such as via an RF link (e.g., at microwavefrequencies, in one embodiment), so all transmissions by theinterrogator 18 are heard simultaneously by all devices 10 within range.

FIG. 4 illustrates a communications system 36 in accordance with oneembodiment of the invention. The communications system 36 includes ananalog to digital converter 38 coupled to the integrated circuit 12. Theanalog to digital converter 38 is external of the single die integratedcircuit 12.

The integrated circuit 12 has a digital input 40. The analog to digitalconverter 38 has a digital output 42 coupled to the digital input 40 ofthe integrated circuit 12. The analog to digital converter 38 has firstand second analog inputs 44 and 46 coupled to an analog measuring device48 such as a temperature sensor, water level sensor, pressure sensor, orany other sensor that produces a voltage. The analog to digitalconverter 38 provides at its digital output 42 a signal indicative ofthe difference between first and second voltages applied to the firstand second analog inputs 44 and 46.

The communications system 36 further comprises transient voltageprotection circuitry 50 coupled between the analog inputs 44 and 46. Thetransient voltage protection circuitry 50 protects the analog inputs′maximum ratings from being exceeded. By using transient voltageprotection circuitry 50, the effects of ESD (Electro-Static Discharge),voltage transients, and induced electrical noise (from the use oflengthy wire connections) can be reduced, and circuit performance can beenhanced.

The integrated circuit 12 further has a clock output 51, and the analogto digital converter 38 has a clock input 53 coupled to the clock output51.

The analog to digital converter 38 further has a chip select input 54which, when triggered, initiates an analog to digital conversion.

The integrated circuit 12 further has a wakeup output 52, coupled to thechip select input 54. A signal is produced at the wakeup output 52 totrigger the chip select input 54 in response to the receiver 32 (ofFIG. 1) receiving a wireless communication. In response to the receiver32 (of FIG. 1) receiving a read digital input command from theinterrogator 18, the integrated circuit 12 (of FIG. 4) provides a signalat the wakeup output 52 and reads the digital input 40.

The analog to digital converter 38 transmits a signal indicative of thevoltage differential at the analog inputs 44 and 46, using thebackscatter transmitter 30 (of FIG. 1), in response to a read digitalport command by the interrogator 18. More particularly, after theinterrogator 18 transmits a read digital port command, the analog todigital converter initiates an analog to digital conversion of thedifference in voltages at the analog inputs 44 and 46. The digitalconversion is read by the integrated circuit 12 and transmitted usingthe backscatter transmitter 30.

The analog to digital converter 38 has a voltage supply input 56, aground connector 57, and a reference voltage input 59. In oneembodiment, the communications system 36 further comprises a voltageregulator 58 coupled to the reference voltage input 59 and to thevoltage supply input 56. The voltage regulator 58 increases accuracy ofthe digital output by providing a stable voltage supply as well asdecreased power consumption. In an alternative embodiment, the voltageregulator 58 is omitted.

In the illustrated embodiment, the integrated circuit 12 is a MicrostampEngine SOIC ™ integrated circuit, part number MSEM256X10SG availablefrom Micron Communications, 3176 S. Denver Way, Boise, Id. 83705, andhas the following pin assignments (not shown): a pin 2 defines thewakeup output 52; a pin 18 defines the clock output 51; and a pin 17defines the digital input 40. Also, in the illustrated embodiment, theanalog to digital converter 38 is an analog to digital converterintegrated circuit, part number LTC1197 available from Linear TechnologyCorporation, and has the following pin assignments: a pin 1 defines thechip select input 54; a pin 2 defines the analog input 44; a pin 3defines the analog input 46; a pin 4 defines the ground connector 57; apin 5 defines the reference voltage input 59; a pin 6 defines thedigital output 42; a pin 7 defines the clock input 53; and a pin 8defines the voltage supply input 56. Other analog to digital converterscan be employed. Also, in one embodiment that includes the voltageregulator 58, the voltage regulator 58 is a Micropower VoltageRegulator™, part number MC78LC50 available from Motorola, and has thefollowing pin assignments: a pin 1 defines a ground connector; a pin 2defines an input 68; and a pin 3 defines an output 70 (FIG. 4). As shownin FIG. 4, a capacitor 72 is coupled between the input 68 and ground;and a capacitor 74 is coupled between the output 70 and ground. In theillustrated embodiment, the capacitors 72 and 74 respectively havevalues of 0.1 μF. The input 68 is coupled to a voltage supply 76 and apull-up resistor 78 is coupled between the voltage supply 76 and thewakeup output 52. In the illustrated embodiment, the resistor 78 has avalue of 100 kΩ. A resistor 80 is shown coupled between the digitaloutput 42 and digital input 40. In the illustrated embodiment, theresistor 80 has a value of 10 kΩ. In the illustrated embodiment, thetransient voltage suppressor 50 is a Transorb ™ surge suppressor.

In one embodiment, the communications system 36 further includes abinary counter 62 coupled between the wakeup output 52 and the chipselect input 54. The binary counter 62 causes the integrated circuit 12to receive from the analog to digital converter 38 multiple conversionsfrom analog to digital per trigger signal. In an alternative embodiment,the binary counter 62 is omitted and the wakeup output 52 is coupled tothe chip select input 54.

In embodiments where the binary counter 62 is employed, one circuitconfiguration that can be employed is shown in FIG. 5. Otheralternatives are possible. The binary counter 62 shown in FIG. 5includes an integrated circuit 80. The integrated circuit 80 includes aload input 82 and a VCC voltage supply input 84 coupled to the voltagesupply 76, enable T and enable P inputs 86 and 88 (only one is used,however they are tied together so there is no pin which is floating), aclear input 90, a clock input 92 coupled to the clock output 51, aground terminal 94 coupled to ground, and a ripple carry output 96. Inthe illustrated embodiment, the integrated circuit 80 is a synchronousbinary counter with asynchronous clear, part number MM74HC161 availablefrom National Semiconductor, and has the following pin assignments: apin 1 defines the clear input 90; a pin 2 defines the clock input 92; apin 7 defines the enable P input 88; a pin 8 defines the ground input94; a pin 9 defines the load input 82; a pin 10 defines the enable Tinput 86; a pin 15 defines the ripple carry output 96, and a pin 16defines the voltage supply input 84. Other integrated circuits could beemployed.

The binary counter 62 further includes a NAND gate 98 having inputs 100and 101 both coupled to the wakeup output 52 and having an output 102coupled to the enable T input 86, the enable p input 88, and the clearinput 90. The binary counter 62 further includes a NAND gate 104 havinginputs 106 and 108 both coupled to the ripple carry output 96 and havingan output 110. The binary counter 62 further includes a NAND gate 112having an input 114 coupled to the output 110 of the NAND gate 104,having an input 116 coupled to the output 102 of the NAND gate 98, andhaving an output 118 coupled to the input 54 of the analog to digitalconverter 38. The clock output 51 is also coupled to the clock input 53of the analog to digital converter 38 of FIG. 4 as it would be if thebinary counter 62 were omitted. Also, if the binary counter 62 wereomitted, the wakeup output 52 would be coupled directly to the chipselect input 54 of the analog to digital converter 38. To save costs,instead of using inverters or some other variety of components, anintegrated circuit having four NAND gates is used to define the NANDgates 98, 104, and 112. In the illustrated embodiment, the integratedcircuit used to define the NAND gates 98, 104, and 112 is a MM74HC00integrated circuit available from National Semiconductor.

By using the binary counter 62, thirty-two conversions from analog todigital are possible per RF command from the interrogator to read thedigital port of the integrated circuit 12. Otherwise, there would onlybe one sample per RF command. With the thirty-two samples, averaging canbe performed to obtain a more accurate reading. In the illustratedembodiment, every two bytes read by the integrated circuit 12 initiatesa conversion stroke from analog to digital. With the binary counter 62,sixty-four bytes are available, resulting in thirty-two conversions.

Another aspect of the invention provides a method of manufacturing andusing the communications system 36 (of FIG. 4). The method comprisessupporting the monolithic semiconductor integrated circuit 12 from asubstrate. The substrate can be a circuit board or other sheet capableof supporting integrated circuits thereon. In the illustratedembodiment, the substrate comprises a plastic sheet 66 that makes up aportion of the housing 28. Alternative substrates are possible (FIG. 2).

The microstrip antenna 15 (of FIG. 2) is supported from the substrate66, external of the integrated circuit 12, and the microstrip antenna 15is electrically coupled to the receiver 32. For example, in oneembodiment, printed thick film is printed on the substrate to define theantenna 15 and intersects a pin on the integrated circuit 12 forelectrical coupling to the receiver 32.

The microstrip antenna 14 is supported from the substrate 66, externalof the integrated circuit 12, and the microstrip antenna 14 iselectrically coupled to the transmitter 30. For example, in oneembodiment, printed thick film is printed on the substrate to define theantenna 15 and intersects a pin on the integrated circuit 12 forelectrical coupling to the receiver 32 as described in commonly assignedU.S. patent application Ser. No. 08/800,037, filed Feb. 13, 1997, nowU.S. Pat. No. 5,988,510.

The battery 16 is supported from the substrate, and electrically coupledto the integrated circuit 12 to supply operating power to the integratedcircuit 12.

The analog to digital converter 38 is coupled to the integrated circuit12. In one embodiment, the analog to digital converter 38 is coupled tothe integrated circuit 12, and the battery 16 is coupled to theintegrated circuit substantially at the same time by mounting the analogto digital converter 38, battery 16, and integrated circuit 12 ontotraces (e.g., printed thick film in one embodiment) drawn on thesubstrate 66 or circuit board. Assembly can take place in a mannersimilar to that disclosed in commonly assigned U.S. patent applicationSer. No. 08/800,037, filed Feb. 13, 1997, now U.S. Pat. No. 5,988,510.

A digital signal indicative of the difference in magnitudes of thevoltages at the analog inputs 44 and 46 is transmitted from theintegrated circuit 12 to the interrogator 18 using the backscattertransmitter 30.

Thus, a communications system is provided where measurements from analogdevices can be transmitted over a range longer than is possible withmagnetic coupling by using an integrated circuit having amicroprocessor, receiver, memory, and backscatter transmitter.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

1. A communications system comprising: an integrated circuit including aprocessor, a receiver coupled to the processor, and a backscattertransmitter coupled to the processor, the integrated circuit having adigital input, and the receiver being configured to receive wirelesscommunications from a remote interrogator; and an analog to digitalconverter external of the integrated circuit, having a digital outputcoupled to the digital input of the integrated circuit, and having ananalog input configured to be coupled to an analog measuring device,wherein the integrated circuit is configured to transmit a signalindicative of the analog input.
 2. A communications system in accordancewith claim 1 wherein the analog input is configured to receive a firstvoltage from the analog measuring device, wherein the analog to digitalconverter further has a second analog input configured to receive asecond voltage, and wherein the analog to digital converter provides atits digital output a signal indicative of the difference between thefirst and second voltages.
 3. A communications system in accordance withclaim 2 and further comprising a transient voltage protector coupledbetween the second analog input and the first mentioned analog input. 4.A communications system comprising: a radio frequency identificationdevice including a first integrated circuit having a processor, areceiver coupled to the processor, a backscatter transmitter coupled tothe processor, the integrated circuit having a digital input, thereceiver being configured to receive wireless communications from aremote interrogator; and an analog to digital converter integratedcircuit having a digital output coupled to the digital input of thefirst integrated circuit, having an analog input configured to becoupled to an analog device, and having a chip select input which isconfigured to initiate, when triggered, an analog to digital conversion,wherein the radio frequency identification device is configured totransmit a signal indicative of the analog input using the backscattertransmitter, and wherein the first integrated circuit has a wakeupoutput, coupled to the chip select input, at which a signal is producedconfigured to trigger the chip select input in response to the receiverreceiving a wireless communication.
 5. A communications system inaccordance with claim 4 wherein, in response to the receiver receiving aread digital input command, the integrated circuit is configured toprovide a signal at the wakeup output and to read the digital input. 6.A communications system in accordance with claim 4 wherein the analog todigital converter has a voltage supply input, and wherein thecommunications system further comprises a voltage regulator coupled tothe voltage supply input.
 7. A communications system comprising: anintegrated circuit having a single die including a processor, a receivercoupled to the processor, and a backscatter transmitter coupled to theprocessor, the integrated circuit having a digital input, the receiverbeing configured to receive wireless commands from a remoteinterrogator; an analog to digital converter external of the single dieand having a digital output coupled to the digital input of theintegrated circuit, having an analog input configured to be coupled toan analog device, and having a chip select input which is configured toinitiate, when triggered, an analog to digital conversion, wherein theradio frequency identification device is configured to transmit adigital signal indicative of the analog input using the backscattertransmitter, and wherein the integrated circuit has a wakeup output atwhich a trigger signal is produced configured to trigger the chip selectinput in response to the receiver receiving a predetermined-wirelesscommand; and a binary counter coupled to the wakeup output and to thechip select input.
 8. A communications system in accordance with claim 7wherein the binary counter between the wakeup output and the chip selectinput causes the integrated circuit to receive from the analog todigital converter multiple conversions from analog to digital pertrigger signal.
 9. A communications system in accordance with claim 8wherein the analog input is configured to receive a first voltage fromthe analog device, wherein the analog to digital converter further has asecond analog input configured to receive a second voltage, and whereinthe analog to digital converter provides at its digital output a signalindicative of the difference between the first and second voltages. 10.A communications system in accordance with claim 9 and furthercomprising a transient voltage protection circuit coupled between thesecond analog input and the first mentioned analog input.
 11. Acommunications system in accordance with claim 8 wherein the analoginput is configured to receive a first voltage from the analog device,wherein the analog to digital converter further has a second analoginput configured to receive a second voltage, wherein the communicationssystem further includes an analog device having first and second analogoutputs respectively coupled to the first mentioned analog input and tothe second analog input, and wherein the analog to digital converterprovides at its digital output a signal indicative of the differencebetween the first and second voltages.
 12. A communications system inaccordance with claim 7 and further comprising an analog measuringdevice coupled to the analog input.
 13. A communications system for usewith a remote interrogator, the system comprising: a wirelesscommunication device including: a semiconductor integrated circuit,including a processor, a receiver coupled to the processor, and abackscatter transmitter coupled to the processor, and a digital inputcoupled to the processor, the transmitter being configured to transmitin response to the receiver receiving a carrier signal from aninterrogator; and a power source electrically coupled to the integratedcircuit and configured to generate operating power for thecommunications device; an analog measuring device; and an analog todigital converter external of the integrated circuit and having adigital output coupled to the digital input of the integrated circuit,having an analog input configured to be coupled to the analog measuringdevice, and having a chip select input configured to initiate an analogto digital conversion when triggered, wherein the integrated circuit isconfigured to transmit a digital signal indicative of the analog inputusing the backscatter transmitter.
 14. A communications system inaccordance with claim 13 wherein the integrated circuit has a wakeupoutput, coupled to the chip select input, at which a trigger signal isproduced configured to trigger the chip select input in response to thereceiver receiving a wireless communication.
 15. A communications systemin accordance with claim 14 and further comprising a binary countercoupled between the wakeup output and the chip select input.
 16. Acommunications system in accordance with claim 15 wherein coupling thebinary counter between the wakeup output and the chip select inputresults in the integrated circuit receiving, from the analog to digitalconverter, multiple conversions from analog to digital per triggersignal.
 17. A communications system in accordance with claim 16 whereinthe analog input is configured to receive a first voltage from an analogmeasuring device, wherein the analog to digital converter further has asecond analog input configured to receive. a second voltage, and whereinthe-analog to digital converter provides at its digital output a signalindicative of the difference between the first and second voltages. 18.A communications system in accordance with claim 17 and furthercomprising transient voltage protection circuitry coupled between thesecond analog input and the first mentioned analog input.
 19. Acommunications method comprising: coupling an analog to digitalconverter to an integrated circuit having a processor, a receivercoupled to the processor, and a transmitter coupled to the processor,the integrated circuit having a digital input, and the receiver beingconfigured to receive wireless communications from a remoteinterrogator, the analog to digital converter having a digital outputand having an analog input configured to be coupled to an analogmeasuring device, the coupling of the analog to digital converter to theintegrated circuit comprising coupling the digital output of the analogto digital converter to the digital input of the integrated circuit. 20.A communications method in accordance with claim 19 wherein the analogto digital converter further has a second analog input, and wherein themethod further comprises providing, at the digital output of the analogto digital converter, a signal indicative of the difference betweenvoltages applied to the second and first mentioned analog inputs.
 21. Acommunications method in accordance with claim 20 and further comprisingproviding protection against transient voltages, between the secondanalog input and the first mentioned analog input.
 22. A communicationsmethod comprising: coupling an analog to digital converter to a radiofrequency identification device including an integrated circuit having aprocessor, a receiver coupled to the processor, and a backscattertransmitter coupled to the processor, the integrated circuit having adigital input, and having a wakeup output at which a signal is producedin response to the receiver receiving a wireless communication, and thereceiver being configured to receive wireless communications from aremote interrogator, the analog to digital converter having a digitaloutput, having an analog input, and having a chip select input which isconfigured to initiate, when triggered, an analog to digital conversion,the coupling of the analog to digital converter to the radio frequencyidentification device comprising coupling the digital output of theanalog to digital converter to the digital input of the integratedcircuit and coupling the chip select input to the wakeup output; andcoupling the analog input to an analog sensor.
 23. A communicationsmethod in accordance with claim 22 and further comprising providing,with the integrated circuit, a signal at the wakeup output, and reading,with the integrated circuit, the digital input, in response to thereceiver receiving a read digital input command.
 24. A communicationsmethod in accordance with claim 22 wherein the analog to digitalconverter has a voltage supply input, and wherein the communicationsmethod further comprises coupling a voltage regulator to the voltagesupply input.
 25. A communications method comprising: coupling an analogto digital converter to an integrated circuit having a single dieincluding a processor, a receiver coupled to the processor, and abackscatter transmitter coupled to the processor, the integrated circuithaving a digital input, and having a wakeup output at which a signal isproduced in response to the receiver receiving a wireless communication,and the receiver being configured to receive wireless communicationsfrom a remote interrogator, the analog to digital converter having adigital output, having an analog input, and having a chip select inputwhich is configured to initiate, when triggered, an analog to digitalconversion, the coupling of the analog to digital converter to theintegrated circuit comprising coupling the digital output of the analogto digital converter to the digital input of the integrated circuit andcoupling the chip select input to the wakeup output; coupling the analoginput to an analog measuring device; and causing the integrated circuitto receive, from the analog to digital converter, multiple conversionsfrom analog to digital per trigger signal.
 26. A communications methodin accordance with claim 25 wherein causing the integrated circuit toreceive, from the analog to digital converter, multiple conversions fromanalog to digital per trigger signal comprises coupling a binary counterbetween the wakeup output and the chip select input.
 27. Acommunications method in accordance with claim 26 wherein the analog todigital converter further has a second analog input, the method furthercomprising providing, at the digital output of the analog to digitalconverter, a signal indicative of the difference between voltagesapplied to the first and second analog inputs.
 28. A communicationsmethod in accordance with claim 27 and further comprising protectingagainst transient voltages between the second analog input and the firstmentioned analog input.
 29. A communications method in accordance withclaim 25 wherein the analog input is configured to receive a firstvoltage from the analog measuring device, wherein the analog to digitalconverter further has a second analog input, wherein the communicationsmethod further includes respectively coupling first and second analogoutputs of an analog device to the first mentioned analog input and tothe second analog input, and providing, with the analog to digitalconverter, at its digital output, a signal indicative of the differencebetween the first and second voltages.
 30. A method of manufacturing andusing a communications system with a remote interrogator unit, themethod comprising: coupling a battery to an integrated circuit includinga processor, a receiver coupled to the processor, a transmitter coupledto the processor, a wakeup output configured to produce a trigger signalin response to the receiver receiving a wireless communication, and adigital input coupled to the processor, the transmitter being configuredto transmit in response to the receiver receiving a carrier signal froman interrogator; and coupling an analog to digital converter to theintegrated circuit, the analog to digital converter having a digitaloutput, having an analog input configured to be coupled to an analogvoltage, and having a chip select input which, when triggered, initiatesan analog to digital conversion, the coupling of the analog to digitalconverter to the integrated circuit comprising coupling the digitaloutput to the digital input.
 31. A method in accordance with claim 30and further comprising coupling the wakeup output to the chip selectinput; and transmitting a digital signal indicative of the analog inputusing the transmitter.
 32. A method in accordance with claim 31 andfurther comprising coupling a binary counter between the wakeup outputand the chip select input.
 33. A method in accordance with claim 32wherein coupling the binary counter between the wakeup output and thechip select input results in the integrated circuit receiving, from theanalog to digital converter, multiple conversions from analog to digitalper trigger signal.
 34. A method in accordance with claim 33 wherein theanalog input is configured to receive a first voltage from an analogmeasuring device, wherein the analog to digital converter further has asecond analog input configured to receive a second voltage, and whereinthe analog to digital converter provides at its digital output a signalindicative of the difference between the first and second voltages. 35.A method in accordance with claim 34 and further comprising a transientvoltage protection circuit coupled between the second analog input andthe first mentioned analog input.
 36. A method comprising: measuring aparameter with an analog sensor to produce one of a voltage and currentsignal indicative of the magnitude of the parameter; converting thesignal to a digital value; reading the digital value with a digitalinput of a wireless communications device having an integrated circuitincluding a processor, a receiver coupled to the processor, atransmitter coupled to the processor, the transmitter being configuredto transmit in response to the receiver receiving a carrier signal froman interrogator; and transmitting the digital value to a remoteinterrogator using the transmitter by modulating onto a carriertransmitted by the interrogator.